CURIOUS MINERALS
FOUND IN SAUDI CAVES

Professor Paolo
Forti, former president of the U.I.S. (International Union of Speleology),
visited several of Saudi Arabia’s limestone
caves in 2003 at the invitation of the Saudi Geological Survey (SGS).
Although the purpose of his visit was to assist the SGS in evaluating
these underground caverns for possible development into tourist caves,
he was also interested in investigating what kind of secondary minerals
might be found in Saudi Arabia’s caves, since few studies of this sort
have been carried out in the Kingdom. Tourist caves will add to the
many other natural attractions of this country leading even more people
to look for hotel deals in Saudi Arabia.

As co-author of the
book Cave Minerals of the World, Prof. Forti is recognized as an authority in
this field. So, it is no surprise that he returned to Italy weighed down with
many small samples taken from Saudi Arabia’s limestone caves as well as from
lava-tube caves, which are found in many of the kingdom’s lava fields or
harrats. Whereas limestone caves are formed by the gradual dissolving of
limestone by slightly acidic rainwater, lava tubes are formed when the surface
of a lava flow begins to harden and the molten lava underneath drains away,
leaving tunnels which, in some cases, can be many kilometers in length.

Upon his return
to Italy, Prof. Forti submitted the samples taken from stalactites,
stalagmites, sediments, etc. for detailed analysis by stereoscopic microscope,
X-ray powder diffractometer, Gandolfi camera and electron scanning microscope
and microprobe.

Several months
later came the results. To Prof. Forti’s surprise, the samples contained not
only the expected minerals, such as calcite and gypsum, but a great variety of
other minerals rarely found in caves, including the following:

GLAUBERITE

This is a hard,
nearly transparent mineral consisting of sulphates of soda and lime. It is
named for one of its components called Glauber’s Salt after a German chemist.
Glauber’s Salt is used in the manufacture of paper and glass and in stomach
medications to aid digestion. Curiously, Glauberite is famous for “not being
present,” which means it often vanishes because it is soluble in water,
casting its unique shape in other minerals and leaving behind only what is
called a pseudomorph.

Glauberite is
found in such diverse locations as Russia, Kenya and Sicily, but has never
been identified in caves before, with the exception of volcanic caves on
Surtsey Island in Iceland. The first identification of this mineral in a
limestone cave –anywhere in the world– was made from a sample found in Saudi
Arabia's B31 Cave located on
the Summan Plateau, 250 kms N of Riyadh.

Paolo
Forti looking for strange minerals like Glauberite in B31 Cave, which normally serves as our
base camp when we're on the Summan Plateau.

ARCANITE

This mineral was
first identified in 1845 in the form of yellow crystals in a pine railroad tie
in tunnel #1 of the Santa Ana tin mine of Orange County, California. The
medieval Latin alchemical name for Arcanite is Arcanum duplicatum, which means
“double secret,” perhaps suggesting that the mineral can only be found in
hidden places. This unusual name is no doubt responsible for fictional “uses”
of arcanite elaborated in fantasy novels, where arcanite is described as the
best possible material for making magic swords, chain mail, etc. Readers of
such stories might be surprised to find that the most likely origin of
arcanite is bat urine.

Previously,
arcanite had only been identified in five caves around the world, all of them
in Africa. Prof. Forti’s team, however, found it in four different samples
taken from Hibashi Cave, an extensive lava tube in Harrat Nawasif-Buqum,
where we have had many an adventure...

Arcanite
was found in the dry bat guano you can see inside this ancient channel through
which lava once flowed...

...And there's arcanite in the thin black coating
found on parts of Hibashi Cave's ceiling. Presumably, this
coating was deposited by smoke from a guano fire.

Mahmoud Al-Shanti and
the shiny black substance on the ceiling.

...It is also found in what we explorers of this cave are calling “stickytites.”
These are soft, tan-colored, organic “stalactites” up to four centimeters
long, which appear to have grown in places where bats made it a habit to
urinate.

They may resemble
daggers (if you have a lot of imagination) but these mini magic swords are
more like "disgusting" than deadly.

PALYGORSKITE

Palygorskite is a clay which is not only rare, but also quite funny looking. Here
is a photo of it, courtesy of
mineral.galleries.com, plus a description of it taken from Cave Minerals of the World by Carol Hill and Paolo Forti:

"This palygorskite is dark, spongy and
slimy, rather like wet leather or fungus, and for this reason it is sometimes
called “mountain leather” by cavers.

In the caves of the Pend Oreille
mining district, northwestern Washington, palygorskite has also been reported
as a leathery deposit and was described humorously by Frost (1971):

White to dirty gray in color
resembling crumpled dirty rags or saggy chewed up cardboard… The grimy
cloth-like appearance creates interest amongst the miners, one of who told me
that he made a pair of underwear out of the stuff."

Palygorskite,
however, is useful for something far more aesthetic than underwear…

THE
MYSTERY OF MAYA BLUE

According to
researchers in the department of chemistry at the University of Texas, El
Paso, palygorskite is the secret ingredient that allowed the Mayan Indians to
produce a blue pigment of great beauty and unprecedented resistance to acids,
alkalis, solvents and biodegradation. The origin of Maya Blue, as it is
called, escaped experts for years...

...People thought the origin of
Maya Blue was copper or
lapis lazuli, but in reality, the Mayans had discovered a still unknown way of
synthesizing this paint from palygorskite and indigo. Only with the help of
powerful synchrotron x-rays have researchers discovered that the indigo is
actually inserted into the channels of the palygorskite clay structure,
affording the paint its unusual stability...

Maya Blue colors the headdress of this clay figure dressed as a ballplayer.
He wears a wooden yoke over a heavy belt. Remnants of a yoke like this were
excavated at Tikal. Princeton Art Museum, Princeton, NJ

...Palygorskite
has been identified in samples taken from Surprise, Friendly and B31
caves. All of these are limestone caves located on the Summan Plateau.
According to Paolo Forti, the palygorskite found in these Saudi caves
is unusually pure and this is the first time the mineral has been
recognized as developed inside natural caves.

The
ceiling of Friendly Cave. Photo courtesy of Paolo Forti.

MINERAL SOUP

Of particular
interest to mineralogists is the great variety of minerals found inside
Hibashi Cave. So far, thirteen minerals have been identified, the majority of them
considered rare in caves.

Guano
fires in Hibashi may have helped produce some of the curious minerals. It
is possible these long- smoldering fires were started accidentally, when
visitors set small fires (right) in order to provide themselves with a bit
of light.

The list of Hibashi minerals begins with the nearly
unpronounceable mineral aphthitalite, a rare, natural soluble sulfate
discovered in 1835 at Mt. Vesuvius. At the end of the list is whitlockite, a
rare phosphate mineral which has been found in Martian meteorites and in human
kidney stones and which takes the form of polished red pearls in some caves.

Here is the
complete list of the minerals so far identified in Hibashi cave:

APHTHITALITE

ARCANITE

ARCHERITE

BIPHOSPHAMMITE

CARBONATEHYDROXYLAPATITE

CHLORAPATITE

DOLOMITE

HYDROXYLAPATITE

ILLITE

PYROCOPROITE

PYROPHOSPHITE

UREA

WHITLOCKITE

The study of Saudi
cave minerals has barely begun and we can fully expect the discovery of other
minerals even more curious than those found in the “Hibashi Mineral Minestrone”
above.

The interesting formation on the
right, for example, was only recently discovered. and not yet scrutinized by
the Italian mineralogists. Ah, Paolo, what will you find next?